Potted insert for honeycomb panels

ABSTRACT

An insert for use of attachment in a threaded member, such as a bolt or the like, to a honeycomb panel by the use of epoxy adhesive, the insert being in the form of an unitary elongated metallic member having a generally cylindrical external surface and an integral annular collar position, the external cylindrical surface having a reduced external diameter circumferential recess in the form of a spiral extending from adjacent one end to the other end of the cylindrical member and having an internal threaded recess therein, the external surface being configured to resist pull-out and torque-out when epoxy adhesive has solidified to retain the insert in a panel.

SUMMARY OF THE INVENTION

Honeycomb panels are frequently used for bulkheads, storage compartmentflooring and other applications within the interior of the aircraft.Other applications for honeycomb panels are: aircraft flight controlsurfaces; transportable military shelters; various ground supportequipment; and electronics cabinetry. Honeycomb panels are preferredbecause of their high strength to weight ratio and since they can beeasily constructed to meet configurations required in the aircraftinterior. One problem in connection with the use of honeycomb panels isthat of attaching devices to them. Since the inner core of a honeycombpanel is generally composed of a cellular material with a great amountof open air spaces, a screw or bolt threaded into an opening in a paneldoes not obtain much pullout resistance. For this reason, a standardtechnique for providing means for attachment of a threaded menber, suchas a bolt to a honeycomb panel, has employed the use of various types ofinserts. For background material relating to inserts used in honeycombpanels, reference may be had to the following U.S. Pat. Nos. 3,271,498;2,880,308; and 3,282,015. These patents are merely representative ofdevices used to provide means for attachment of a threaded member to apanel. In these prior issued patents, the typical panel to which theyare applied are referred to as "Sandwich Panels", however, it isunderstood that by the term "sandwich" is meant panels of the type whichinclude a honeycomb interior.

The insert as described in the present disclosure has advantages overthose illusrated in these previously issued United States Patents inthat the insert herein described has a greater pull-out and torque-outresistance, and, therefore, provides increased resistance to failure.

The insert of this disclosure is in the form of an elongated metallicmember having a generally cylindrical external surface. The member hasan outer end and an inner end.

Formed as part of the external cylindrical surface at the outer end isan integral annular collar portion. Adjacent the collar portion is areduced external diameter circumferential recess which is contiguous tothe collar portion.

Also formed on the generally cylindrical external surface of the memberis a spiraled recess communicating at one end with the circumferentialrecess and extending to adjacent the member inner end.

Opposed notches are provided in the annular collar portion communicatingthe element outer end with the circumferential recess.

An internal threaded recess is formed in the element, the threadedrecess being coaxial with this axis of the member cylindrical externalsurface and extending from the outer end to adjacent the inner end.

In a preferred arrangement of the invention, the spiral recess formed inthe generally cylindrical external surface is defined by substantiallyparalleled opposed walls.

A better understanding of the invention will be had by reference to thefollowing description and claims, taken in conjunction with the attacheddrawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external evelational view of one embodiment of the elementof this disclosure.

FIG. 2 is an end view of the inner end of the element of FIG. 1.

FIG. 3 is an external elevational view of an alternate embodiment of theelement of this disclosure.

FIG. 4 is an end view of the inner end of the element of FIG. 3.

FIG. 5 is a third embodiment of an element employing the principles ofthis invention.

FIG. 6 is an end view of the element of FIG. 5.

FIG. 7 is an elevational partial cross-sectional view of the element ofFIG. 1, showing in more detail the internal threaded recess.

FIG. 8 is a partial cross-sectional view of a honeycomb panel having anelement of the present disclosure retained within the panel as anillustration of the means of making use of the insert.

FIG. 9 is a partial cross-sectional view of a honeycomb panel having theelement of FIGS. 5 and 6 retained within the panel.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1, 2, 7 and 8, a first embodiment of the element ofthe invention is illustrated, the element being generally indicated bythe numeral 10. The element 10 is a metallic member, such as formed ofstainless steel, aluminum alloy, carbon steel, or the like. The member10 has an inner end 12 and an outer end 14. The element 10 has agenerally cylindrical surface 16.

A circumferential recess 18 is formed in the outer cylindrical surface16 adjacent to and spaced from the inner end. This circumferentialrecess provides an integral annular collar portion 20.

The external cylindrical surface 16 is further defined by a spiraledgroove 22 which extends from the circumferential recess 18 to adjacentthe outer end 14. The spiral groove 22 and the annular recess 18 areboth formed preferably with parallel sidewalls, that is, wherein thesidewalls 24A and 24B of the circumferential recess 18 are in planeperpendicular to the element cylindrical axis. In like manner, thespiral groove 22 is preferably formed, as illustrated, wherein thesidewalls 26A and 26B are parallel to each other.

The annular collar portion 20 is provided with opposed notches 28A and28B.

Formed in the element and communicating with the inner end 12 is aninternally threaded recess 30 which is adapted to receive a threadedbolt or other retention member.

As shown in FIG. 7, the element 10 includes a small diameter radialopening 32 communicating with the internal threaded recess 30 and theexterior of the element at the circumferential recess 18. Positioned inthe radial opening 30 is a locking plug 34 formed of a tough plasticmaterial. The locking plug 34 is pressed or molded into opening 32 sothat the inner end thereof engages any threaded member (not shown) whichis threaded into opening 30. Locking plug 34 serves to resist theinadvertent unthreading of any member threaded into the element, whichis particularly important in aircrafts due to vibration.

FIGS. 3 and 4 show an alternate embodiment of the disclosure in whichthe annular collar portion 20A includes an integal, enlarged externaldiameter flange portion 36. The flange portion 36 includes opposed smalldiameter opening 38A and 38B therethrough.

FIGS. 5 and 6 show an additional alternate embodiment of the disclosurein which the circumferential flange is provided with a circumferenitalgroove 40. In this embodiment, the diameter of the annular collarportion 20B is preferably slightly larger than the generally cylindricalsurface 16.

Referring to FIG. 8, the method of use of the insert is illustrated. Ahoneycomb panel 42 is formed of an inner cellular wall with a firstouter skin 44 and an inner skin 46. In order to provide means forattachment of a threaded member, and opening 48 has been formed in thepanel. The opening has been formed in the typical manner utilizing ahook routing tool, that is, an L-shaped tool (not shown). First, a holeof the required diameter, such as that slightly greater than thediameter of the external cylindrical surface 20 of the element, isformed in the outer skin 46. Then the L-shaped drilling tool is insertedinto the panel past the outer skin 44 to drill the increased diameterhole 48.

To mount the element 10 in the panel, the opening 48 first receives aquantity of epoxy adhesive 50. The element 10 is then inserted throughthe opening 44A formed in the outer skin 40 so that the epoxy 50completely fills the opening 48 between the inner skin 44 and the outerskin 46, and surrounds and contacts all external surfaces of the element10. When the expoxy has hardened, the element is securely mounted withinthe panel 42 and can then receive threaded members, such as for mountingfire extinguishers, brackets, seat track, and so forth.

FIG. 9 shows the use of the embodiment of FIG. 5 and 6 wherein the panelouter skin 44 snaps into the element circumferential recess 40 to holdthe element in place until the epoxy adhesive hardens.

The application of FIG. 3 is not illustrated, but it can be used in sucha way that flange 38 is either flushed with the outer skin 44 or theflange 36 may extend externally of the panel, with the opening in thepanel outer skin 44 being that which is sized to receive the annularcollar portion 20A.

The notches 28A and 28B in the embodiment of FIG. 1, as shown best inFIG. 2, serve to permit the escape of excess epoxy adhesive when theelement is inserted into position. This not only allows for the escapeof excessive material but serves to demonstrate that sufficient epoxyadhesive has been employed so that full contact with all of the outersurface area of the element has been achieved. If additional epoxymaterial is required, it can be inserted through one of the notches 28Awith the other notch 28B used to permit the escape of excessive materialand to demonstrate that the opening in the panel has been completelyfilled with epoxy adhesive.

With reference to FIG. 4, the small diameter openings 38A and 38B servethe same purpose as has been described with respect to notches 28A and28B.

The insert as described provides an improved element for use inconjunction with honeycomb panels. The device is easy to use and doesnot include irregularities on the external surface which may escapecontact with the epoxy adhesive and which provides square shoulderedsurfaces to resist pull-out and torque-out strength is obtained by thedesigns of this disclosure since the spiral groove provides increasedsurface contact area which resist shear of the epoxy embedded in thegrooves when a load is applied. This increase resistance applies to bothconditions, that is, straight pull and torque-out or a combination ofboth.

The claims and the specification describe the invention presented andthe terms that are employed in the claims draw their meaning from theuse of such terms in the specification. The same terms employed in theprior art may be broader in meaning than specifically employed herein.Whenever there is a question between the broader definition of suchterms used in the prior art and the more specific use of the termsherein, the more specific meaning is meant.

While the invention has been described with a certain degree ofparticularity it is manifest that many changes may be made in thedetails of construction and the arrangement of components withoutdeparting from the spirit and scope of this disclosure. It is understoodthat the invention is not limited to the embodiments set forth hereinfor purposes of exemplification, but is to be limited only by the scopeof the attached claim or claims, including the full range of equivalencyto which each element thereof is entitled.

I claim:
 1. An insert for use in attachment of a threaded member, suchas a bolt or the like, to a panel, such as a honeycomb panel, such as byuse of epoxy adhesive, the insert comprising:an unitary elongate memberhaving a generally cylindrical external surface and an outer end and aninner end, and having on the external cylindrical surface at the outerend an integral annular collar portion and having a reduced externaldiameter circumferential recess contiguous to said collar portion, andhaving on the external cylindrical surface a spiraled recesscommunicating at one end with said circumferential recess and extendingadjacent to but not to said inner end, the inner end having a diametersubstantially equal to that of said member cylindrical surface, andhaving opposed notches in said annular collar portion communicating saidouter end with said circumferential recess, and having an internalthreaded recess therein coaxial with said member cylindrical externalsurface and extending from said outer end to adjacent said inner end. 2.An insert according to claim 1 wherein said spiraled recess is definedby substantially paralleled opposed walls.
 3. An insert according toclaim 2 wherein said circumferential recess, said spiraled recess andsaid opposed notches in said annual collar are all of about the samedepth.